The mechanisms involved in the induction and control of the allergic response are not completely understood. The allergic response is known to be effected by antibody-mediated (immediate-type) hypersensitivity, cell-mediated (delayed-type) hypersensitivity, or both.
The antibody which is largely responsible for immediate type hypersensitivity reactions is immunoglobulin E ("IgE"). IgE antibodies bind to the membranes of mast cells in skin or to basophils, specific membrane receptors that recognize and bind the IgE molecule. The binding affinity of these classes of receptors for IgE is very high. A. Nisonoff, Molecular Immunology, p. 55 (1982).
After the IgE antibody is bound to the cell receptor on the mast cell or basophil, an allergen binds to two or more IgE antibodies, causing the mast cells or basophils to release numerous granules. These granules contain the mediators of immediate hypersensitivity. These mediators have extremely potent contractile effects on the smaller airways of the respiratory tract. In mice and rats, serotonin is the principal mediator. In humans, histamine is the most important mediator of immediate hypersensitivity. SRS-A (Slow Reacting Substance of Anaphylaxis) and ECF-A (Eosinophil Chemotactic Factor) are other mediators.
The symptoms of allergies include sinusitis, rhinitis, hives, headaches, post-nasal drip, coughing, sneezing, respiratory difficulties, sore throats, allergic conjunctivitis, tightness in throat and chest, and loss of voice. In extreme cases the allergic response may cause fetal anaphylactic shock. The sneezing and respiratory difficulties are brought on by contractions of smooth muscle of the respiratory tract. The other symptoms are brought on by the inflammation caused by increased vascular permeability and the attraction of leukocytes.
Examples of antibody-mediated hypersensitivity are hay fever, asthma, food allergies and hives. This type of allergy is called atopy and it is characterized by sensitivity without prior exposure to the allergen causative agent. Delayed-type hypersensitivity is mediated by T-cells. Examples of cell-mediated hypersensitivity include allergic contact dermatitis, allergies to drugs, and a number of autoimmune diseases.
Typically, allergies are treated by a variety of drugs aimed at counteracting the symptoms of an allergic reaction. However, these prior treatments are useful only on a short term basis, and often have adverse or disadvantageous and unwanted side effects. For example, antihistamines are often used to alleviate temporarily the general discomfort caused by histamine release. Such drugs, however, cause drowsiness and therefore are not recommended for use during working hours. Corticosteroids are also used to treat severe allergic reactions. However, these compounds immunosuppress the patient and thereby increase his susceptibility to infectious disease. Inhaled salbutamol (known as albuterol in the United Sates) is commonly used by asthma patients. However, like other sympathomimetic agents, salbutamol can have side reactions such as hypertension, angina, vomiting, vertigo, and insomnia.
In view of the disadvantages of such prior allergy treatments, conventional means for treating allergies remain disappointing to the patient, as well as to the clinician. Therefore, the need exists for a process which avoids these disadvantages and provides effective treatment for allergies.